Exploring the accuracy of the equation-of-motion coupled-cluster band gap of solids

TL;DR

This paper introduces a hybrid method combining EOM-CCSD with the GW approximation to accurately estimate band gaps in solids, reducing computational costs and providing new insights into electronic excitations.

Contribution

The study presents a novel hybrid approach that mitigates finite-size errors in EOM-CCSD calculations for solids, enabling more practical and accurate band gap predictions.

Findings

Hybrid EOM-CCSD/GW method reduces required cell sizes.

Deviations in EOM-CCSD correlate with single excitation character.

Method aligns well with experimental and GW results.

Abstract

While the periodic equation-of-motion coupled-cluster (EOM-CC) method promises systematic improvement of electronic band gap calculations in solids, its practical application at the singles and doubles level (EOM-CCSD) is hindered by severe finite-size errors in feasible simulation cells. We present a hybrid approach combining EOM-CCSD with the computationally efficient $GW$ approximation to estimate thermodynamic limit band gaps for several insulators and semiconductors. Our method substantially reduces required cell sizes while maintaining accuracy. Comparisons with experimental gaps and self-consistent $GW$ calculations reveal that deviations in EOM-CCSD predictions correlate with reduced single excitation character of the excited many-electron states. Our work not only provides a computationally tractable approach to EOM-CC calculations in solids but also reveals fundamental insights into the role of single excitations in electronic-structure theory.